/*
 * $Id: PDFOutput.java,v 1.3 2007/09/22 12:48:16 gil1 Exp $ $Date: 2007/09/22
 * 12:48:16 $ This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of the License,
 * or (at your option) any later version. This library is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY; without even the
 * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
 * the GNU Lesser General Public License for more details. You should have
 * received a copy of the GNU Lesser General Public License along with this
 * library; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place, Suite 330, Boston, MA 02111-1307 USA
 */
package pdf.handler;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Vector;

/**
 * This class is used to write a PDF document. It acts as a wrapper to a real
 * OutputStream, but is necessary for certain internal PDF structures to be
 * built correctly.
 * 
 * @author Peter T. Mount
 * @author Eric Z. Beard, ericzbeard@hotmail.com
 * @version $Revision: 1.3 $, $Date: 2007/09/22 12:48:16 $
 */
public class PDFOutput
{
   /**
    * This is the OutputStream used to write each object to.
    * <p>
    * We use a separate stream, because we need to keep track of how many bytes
    * have been written for each object for the xref table to work correctly.
    */
   protected ByteArrayOutputStream baos;

   /**
    * This is used to track the /Info object (info)
    */
   protected PDFObject infoID;

   /**
    * This is the current position within the stream
    */
   protected int offset;

   /**
    * This vector contains offsets of each object
    */
   protected Vector<PDFXref> offsets;

   /**
    * This is the actual OutputStream used to write to.
    */
   protected OutputStream os;

   /**
    * This is used to track the /Root object (catalog)
    */
   protected PDFObject rootID;

   /**
    * This creates a PDF OutputStream
    * 
    * @param os
    *            The output stream to write the PDF file to.
    * @throws IOException
    *             if there is an I/O error.
    */
   public PDFOutput(OutputStream os) throws IOException
   {
      this.os = os;
      offset = 0;
      offsets = new Vector<PDFXref>();
      baos = new ByteArrayOutputStream();

      // Now write the PDF header
      //
      // Note: As the encoding is fixed here, we use getBytes().
      //
      baos.write("%PDF-1.2\n".getBytes());

      // This second comment is advised in the PDF Reference manual
      // page 61
      baos.write("%\342\343\317\323\n".getBytes());

      offset = baos.size();
      baos.writeTo(os);
   }

   /**
    * This closes the Stream, writing the xref table
    */
   protected void close() throws IOException
   {
      // Make sure everything is written
      os.flush();

      // we use baos to speed things up a little.
      // Also, offset is preserved, and marks the begining of this block.
      // This is required by PDF at the end of the PDF file.
      baos.reset();
      baos.write("xref\n".getBytes());

      // Now a single subsection for object 0
      // baos.write("0 1\n0000000000 65535 f \n".getBytes());

      // Now scan through the offsets list. The should be in sequence,
      // but just in case:
      int firstid = 0; // First id in block
      int lastid = -1; // The last id used
      Vector<PDFXref> block = new Vector<PDFXref>(); // xrefs in this block

      // We need block 0 to exist
      block.addElement(new PDFXref(0, 0, 65535));

      for (PDFXref x : offsets)
      {

         if (firstid == -1)
            firstid = x.id;

         // check to see if block is in range (-1 means empty)
         if (lastid > -1 && x.id != (lastid + 1))
         {
            // no, so write this block, and reset
            writeblock(firstid, block);
            block.removeAllElements();
            firstid = -1;
         }

         // now add to block
         block.addElement(x);
         lastid = x.id;
      }

      // now write the last block
      if (firstid > -1)
         writeblock(firstid, block);

      // now the trailer object
      baos.write("trailer\n<<\n".getBytes());

      // the number of entries (REQUIRED)
      baos.write("/Size ".getBytes());
      baos.write(Integer.toString(offsets.size() + 1).getBytes());
      baos.write("\n".getBytes());

      // the /Root catalog indirect reference (REQUIRED)
      if (rootID != null)
      {
         baos.write("/Root ".getBytes());
         baos.write(rootID.toString().getBytes());
         baos.write("\n".getBytes());
      }
      else
         throw new IOException("Root object is not present in document");

      // the /Info reference (OPTIONAL)
      if (infoID != null)
      {
         baos.write("/Info ".getBytes());
         baos.write(infoID.toString().getBytes());
         baos.write("\n".getBytes());
      }

      // end the trailer object
      baos.write(">>\nstartxref\n".getBytes());
      baos.write(Integer.toString(offset).getBytes());
      baos.write("\n%%EOF\n".getBytes());

      // now flush the stream
      baos.writeTo(os);
      os.flush();
   }

   /**
    * This method writes a PDFObject to the stream.
    * 
    * @param ob
    *            PDFObject Obeject to write
    * @exception IOException
    *                on error
    */
   protected void write(PDFObject ob) throws IOException
   {
      // Check the object to see if it's one that is needed in the trailer
      // object
      if (ob instanceof PDFCatalog)
         rootID = ob;
      if (ob instanceof PDFInfo)
         infoID = ob;

      offsets.addElement(new PDFXref(ob.getSerialID(), offset));
      baos.reset();
      ob.write(baos);
      offset += baos.size();
      baos.writeTo(os);
   }

   /**
    * Writes a block of references to the PDF file
    * 
    * @param firstid
    *            ID of the first reference in this block
    * @param block
    *            Vector containing the references in this block
    * @exception IOException
    *                on write error
    */
   protected void writeblock(int firstid, Vector<PDFXref> block)
         throws IOException
         {
      baos.write(Integer.toString(firstid).getBytes());
      baos.write(" ".getBytes());
      baos.write(Integer.toString(block.size()).getBytes());
      baos.write("\n".getBytes());
      // baos.write("\n0000000000 65535 f\n".getBytes());

      for (PDFXref x : block)
      {
         baos.write(x.toString().getBytes());
         baos.write("\n".getBytes());
      }
         }
} // end class PDFOutput
